Best to give the customer what they want, after explaining the options to them. Every client will have different needs and a different budget. If they don't have the budget for SEO when they start, you'd be surprised at how many will upgrade over time, if they know you offer the service. Some will want it all upon starting, but that is rare in my experience.
Any time you can sell or upgrade a client to something with monthly billing, you will be making your business stronger, as you will not have to rely on constantly selling and closing deals. So get them in the door, and then upgrade them.